Was web surfing Yellowstone National Park, which I do on a regular basis all year long. I was in my home office just going through their various web cameras just after 8am in mid to late April. This actually occurred on April 23, 2011 at 8:28 am on the Mt. Washburn webcam, which is at an elevation around 10,100′ give or take a few feet. I was really surprised to see this object on the mountain ridge, and you can see it clearly in the webphoto that I captured at the time. This object was there for a frame or two, then was gone. I have no idea what it was. One thing I am sure of and that is it was not there in June when I hiked the Mt. Washburn trail to the ranger fire lookout tower. I thought this was out of place, and being a meteorologist, at first I thought it was something for observing snowfall/rainfall. But in my 38 years in meteorology, I have never encountered any equipment that looks like this. You can see the object below the fence on the ridge peak. To this day I am still baffled as to what it could be. You can clearly see it is cylindrical in shape, with what appears to be a silver or grey dome shaped top. This object appeared stationary during the few short webframes. This is the only capture I got of it, before realizing that this was definitely out of place. I have no idea what it was, other than what you can see in the photo. I believe YNP archives there webcam photos, so maybe they have more photos of this.